I didnt notice his throat, but Im pretty sure the eyes were done on purpose to give him もっと見る of a dark eyed dead look, and my guess is that some people also thought it would make him look もっと見る attractive. Remember that Dracula is also much older than Angel, so there are bound to be differences.
I can't quite explain the issue with the throat. My guess is it was a last 分 change of costume for the character and they neglected the throat. The dark around the eyes is deliberate, あなた will find a lot of nods to the original novel in that episode and the eyes was one of them. Also Dracula is an extremely pale figure. He's not the typical Buffy vampire. Rudolf Martin, the one playing him, was also playing Dracula that very same 年 for the film Dracula: The Dark Prince and his skin is a bit on the dark side, naturally. Remember, Dracula is from Romania, the land of the gypsy. It's probably only vampirism that keeps him so pale.